With the convenience of mobile network, people can do different kinds of activities, such as payments, shopping, auctions, and so on, whenever and wherever. Electronic commerce (e-commerce) has become so popular that the number of people using these online services has been increasing enormously in recent years. Hence, the security issues of e-commerce and the rights of users in transaction have raised our concerns. Electronic cash (e-cash) is definitely one of the most popular research topics among e-commerce area. It is very important that e-cash has to be able to hold the anonymity and accuracy in order to preserve the privacy and rights of customers. There are two types of e-cash in general, which are online e-cash and offline e-cash. Both systems have their own pros and cons, and they can be used to construct various applications. In this thesis, we propose a provably secure and efficient offline e-cash scheme with date attachability based on blind signature technique, where expiration date and deposit date can be embedded in an e-cash, simultaneously. With the help of expiration date, the bank can manage the huge database much more easily against unlimited growth, and the deposit date cannot be forged so that users are able to calculate the amount of interests they can receive in the future correctly. Furthermore, our scheme maintains the properties of e-cash, which are anonymity control, double-spending checking and unforgeability. We also provide security analysis and formal proofs in this thesis.

Vehicular ad hoc networks (VANETs) are instances of mobile ad hoc networks with the aim to enhance the safety and efficiency of road traffic. The basic idea is to allow arbitrary vehicles to broadcast ad hoc messages (e.g. traffic accidents) to other vehicles and remind drivers to change their route immediately or slow down to avoid dangers. However, some concerns of security and privacy are also raised in this environment. Messages should be signed and verified before they are trusted while the real identities of vehicles should not be revealed to guarantee the source privacy, but it still has to be traceable to prevent any abuse of VANETs (e.g. sending a fake message). Many related works have been presented in the literature so far. They can be generally divided into two constructions, where one is based on pseudonymous authentication and the other is based on group signatures. However, both of the two constructions have some drawbacks. Consequently, in this thesis, we come up with a provably secure and strong privacy preserving protocol based on the blind signature technique to guarantee privacy and fulfill other essential security requirements in the vehicular communication environment. Besides, compared with other similar works, we offer an efficient tracing mechanism to trace and revoke the vehicles abusing the VANETs. In addition, considering the real environment, we also provide simulation results to show that our scheme is more practical, efficient and suitable for VANETs under a real city street scenario with high vehicle density. Finally, we also demonstrate the security of the proposed protocol by formal proofs.

In this thesis, a novel pre-coded direct-sequence code division multiple access (DS-CDMA) associated with the multiple-input multiple-output (MIMO) antennas, along with Alamouti¡¦s space-time block code (ST-BC) is considered. In the transmitter, the idea of hybrid pre-coded is exploited; it can be employed to counteract the inter-symbol interference (ISI) introduced by the channel fading duo to multipath propagation, and can be used to exacting the full information of channel impulse response (CIR) in the receiver for semi-blind channel estimation. Under this transceiver framework, we develop a semi-blind adaptive MIMO-CDMA receiver, based on the linearly constrained constant modulus (LCCM) criterion, for symbol recovery. Furthermore, to reduce the complexity of receiver design, the framework of the generalized sidelobe canceller (GSC) associated with the recursive least-squares (RLS) algorithm is adopted, and the gradient approach is applied to track the desired user¡¦s amplitude, simultaneously, and is named as the GSC-CM-IQRD-RLS algorithm. Via computer simulations, the superior performance and the advantages of proposed scheme is verified; it outperforms the conventional LCMV-based algorithm, and slightly better than the convention CM-GSC-RLS receiver, with the paid of spectral efficient.

Due to the growing interest in electronic commerce, more and more transactions now happen online. Thus, fair transactions between customers and merchants are getting important. To gain the fairness of the exchange of digital items, fair exchange protocols have been proposed and well studied. Most of the traditional fair exchange protocols are concerned about the exchange of digital items, such as digital signatures, contracts, and documents. Recently, researchers pay attention to the exchange of digital goods along with electronic cash, and have proposed some fair transaction protocols based on electronic cash. To buy digital contents via electronic cash through network, the anonymity property as traditional cash possesses must be guaranteed. It means that the payment information of the customer cannot be revealed to anyone else including the trusted third party (TTP) who helps the customer and the merchant with resolving possible disputes in the protocol. Since the customer and the merchant may not trust each other in an electronic transaction. In a fair exchange protocol, a TTP is employed to achieve true fairness. An on-line TTP has to take part in all transactions while they are proceeding. Despite it can gain true fairness, it is inefficient due to on-line interaction with the TTP. On the other hand, an off-line TTP does not need to join in the transaction protocol in normal cases. Instead, it participates in the protocol only when disputes happen. It is efficient and fair, and more feasible in practical situations. In this thesis, we propose a fair transaction protocol based on electronic cash. With the extended research on electronic cash, we have designed a fair transaction protocol that is suitable for any electronic cash system. By using an off-line TTP, the protocol is more efficient and practical. Furthermore, payment information of the customer cannot be known to anyone else including the TTP, and thus, the anonymity of the customer is protected completely in our protocol.

The technology of electronic cash makes it possible to transmit digital money over communication networks during electronic transactions. Owing to the untraceability and unforgeability properties, electronic cash can protect the privacy of customers and guarantee the security of payments in the transactions. This manuscript introduces an efficient electronic cash protocol where it only requires minimal storage for each customer to withdraw w dollars from the bank and spend the w dollars in a sequence of transactions. Compared with traditional electronic cash protocols, the proposed method greatly reduces not only the storage required for the customers but the communication traffic in the transactions as well. Furthermore, the computation cost of the entire protocol is lower than the traditional ones and it also achieves the customer efficiency property. It turns out that the proposed protocol is much more suitable for the storage-limited or hardware-limited environments, such as smart card computing or mobile commerce, than the traditional electronic cash protocols in a sequence of payments. In addition, we examine the security of the proposed electronic cash protocol from the customer¡¦s, the shop¡¦s, and the bank¡¦s points of view, respectively. Since the proposed protocol is based on a generic partially blind signature scheme, it can be implemented by any partially blind signature scheme as long as it is secure and user efficient.

Due to convenience and efficiency, electronic voting (e-voting) techniques gradually replace traditional paper-based voting activities in some developed countries. A secure anonymous e-voting system has to satisfy many properties, such as completeness, tally correctness, and uncoercibility, where the uncoercibility property is the most difficult one to be achieved. Since each voter can obtain a voting receipt in an electronic voting system, coercion and bribe (vote-buying and vote-selling are included) become more and more serious in electronic voting environments than traditional paper-based voting environments. Unfortunately, most of the solutions, like receipt-freeness or untappable channels, proposed in the literature, are impractical owing to lack of efficiency or too complicated to be implemented. It will make uncoercible e-voting systems unacceptable by the people. In order to cope with the drawbacks of the previous schemes, this thesis will present a generic idea, which is independent of the underlying cryptographic components, on electronic voting to achieve the uncoercibility property and other requirements. The proposed method is an efficient and quite practical solution to match the current environments of electronic voting.

Thesis (Ph. D.)--Open University. BLDSC no. DX179937.

Color is used in everything we see and do and it often can be used for effect and representation, particularly on maps and transportation signage. This study explores the issues that the color blind population exhibits when viewing these maps and signs. Seeing that 8%#37; of the male population is afflicted with some form of color blindness, it is pertinent that research reflect these issues and take into consideration the Right to Receive Information for this population. A qualitative method using Photovoice and interviews was used to determine whether this population considers itself having a disability and what solutions can be found to assist with issues of seeing colors on transportation maps and signage. Results show that although half of the participants feel they have a disability, they do not want to be categorized with other disabilities or have restrictions placed on them. The overall consensus regarding maps was to use less colors and simplify. One solution to the issue of being able to read maps and signage was to instill the ColorADD Symbol System in the U.S. comprehensively. This study provides insight to the issues faced by the color blind population regarding Right to Receive Information for maps and signage, including alternate solutions to providing color blind people with sufficient materials. The significance of this research can be used to provide safer transportation signage for driving and better maps for traveling.

This thesis presents the research carried out to investigate and achieve highly reliable and accurate navigation system of guidance for visually impaired pedestrians. The main aim with this PhD project has been to identify the limits and insufficiencies in utilising Network Real-Time Kinematic Global Navigation Satellite Systems (NRTK GNSS) and its augmentation techniques within the frame of pedestrian applications in a variety of environments and circumstances. Moreover, the system can be used in many other applications, including unmanned vehicles, military applications, police, etc. NRTK GNSS positioning is considered to be a superior solution in comparison to the conventional standalone Global Positioning System (GPS) technique whose accuracy is highly affected by the distance dependent errors such as satellite orbital and atmospheric biases. Nevertheless, NRTK GNSS positioning is particularly constrained by wireless data link coverage, delays of correction and transmission and completeness, GPS and GLONASS signal availability, etc., which could downgrade the positioning quality of the NRTK results. This research is based on the dual frequency NRTK GNSS (GPS and GLONASS). Additionally, it is incorporated into several positioning and communication methods responsible for data correction while providing the position solutions, in which all identified contextual factors and application requirements are accounted. The positioning model operates through client-server based architecture consisted of a Navigation Service Centre (NSC) and a Mobile Navigation Unit (MNU). Hybrid functional approaches were consisting of several processing procedures allowing the positioning model to operate in position determination modes. NRTK GNSS and augmentation service is used if enough navigation information was available at the MNU using its local positioning device (GPS/GLONASS receiver).The positioning model at MNU was experimentally evaluated and centimetric accuracy was generally attained during both static and kinematic tests in various environments (urban, suburban and rural). This high accuracy was merely affected by some level of unavailability mainly caused by GPS and GLONASS signal blockage. Additionally, the influence of the number of satellites in view, dilution of precision (DOP) and age corrections (AoC) over the accuracy and stability of the NRTK GNSS solution was also investigated during this research and presented in the thesis. This positioning performance has outperformed the existing GPS service. In addition, utilising a simulation evaluation facility the positioning model at MNU performance was quantified with reference to a hybrid positioning service that will be offered by future Galileo Open Service (OS) along with GPS. However, a significant difference in terms of the service availability for the advantage of the hybrid system was experienced in all remaining scenarios and environments more especially the urban areas due to surrounding obstacles and conditions. As an outcome of this research a new and precise positioning model was proposed. The adaptive framework is understood as approaching an integration of the available positioning technology into the context of surrounding wireless communication for a maintainable performance. The positioning model has the capability of delivering indeed accurate, precise and consistent position solutions, and thus is fulfilling the requirements of visually impaired people navigation application, as identified in the adaptive framework.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / Multipath interference continues to be the dominant cause of telemetry link outages in low-elevation angle reception scenarios. The most reliable and universally applicable solution to this problem is in the form of equalization. Previous work in this area has considered the Constant modulus algorithm (CMA) equalizer operating in a blind adaptive mode. To the extent that knowledge of the multipath channel improves the performance of CMA and related equalizers and permits the use of other equalization techniques, data aided equalizers are of interest. Channel knowledge is obtained by comparing the received samples with the samples corresponding to a known bit pattern (called a pilot block) periodically inserted in the telemetry data stream. The main objective of this research is to evaluate the performance of a modified CMA equalization algorithm, which has the property of automatically resolving the phase of the QPSK modulated symbol, and to determine its suitability for use with SOQPSK-TG by taking into account the capability of exploiting the presence of a periodically inserted pilot block. As an initial effort in that direction, this paper provides simulation results of the error performance of the blind linear combination of CMA and alphabet matched algorithm (AMA) equalizer as compared to that of pilot assisted equalization with SOQPSK modulation over aeronautical channel.